1. Field of the Invention
The present invention relates to an operating lever device, and more particularly to an operating lever device capable of retaining output signals of an operating lever.
2. Description of the Related Art
There are already inventions concerning operating lever devices for generating an operating signal by the tilting of a single operating lever, and driving two hydraulic actuators in a controlled manner on the basis of this operating signal.
For example, Japanese Patent Application Laid-open No. 9-89515 discloses an electric operating lever device for outputting displacement as an electrical signal to each of four pistons by tilting an operating lever. Two hydraulic actuators can be driven in a controlled manner on the basis of electrical signals outputted by this electric operating lever device.
In addition, the international publication No. WO96/15374 discloses a hydraulic operating lever device for outputting hydraulic signals.
FIG. 12(a) depicts a fragmentary cross section of a hydraulic operating lever device. Displacement is outputted as an electrical signal to each of four pistons by tilting an operating lever.
FIG. 12(b) is a perspective view depicting the structure of the universal joint 50 shown in FIG. 12(a). Two hydraulic motors mounted on a hydraulically driven vehicle are driven in a controlled manner by the operating lever device in FIGS. 12(a) and 12(b). In addition, FIGS. 13(a) and 13(b) show the manner in which the operating lever shown in FIGS. 12(a) and 12(b) is moved around. A description will now be given with reference to these drawings.
The operating lever device 5 shown in FIG. 12(a) primarily comprises a device unit 7 and an operating lever 6 tiltably provided to the device unit 7.
The operating lever 6 is mounted on the device unit 7 through the agency of a universal joint 50 and a disk plate 8.
As shown in FIGS. 13(a) and 13(b), four pistons 1, 2, 3, and 4 are provided such that piston tips (tops) project from a mounting plate 11. Viewed from above the mounting plate 11, the pistons 1, 2, 3, and 4 are arranged in the four corners of a square. The vehicle is propelled forward by the tilting of the operating lever 6 in the F-direction and pushing down the piston 4. The vehicle is propelled backward by the tilting of the operating lever 6 in the B-direction and pushing down the piston 2. The vehicle is caused to spin-turn to the right by the tilting of the operating lever 6 in the R-direction and pushing down the piston 1. The vehicle is caused to spin-turn to the left by the tilting of the operating lever 6 in the L-direction and pushing down the piston 3. As used herein, "spin-turn" is occasionally referred to as pirouetting. This is a movement in which a vehicle turns while the center of the vehicle remains stationary. In more-specific terms, this is an operation in which a turn is performed by causing the wheels or tracks provided to the vehicle to rotate at the same speed but in mutually opposite directions.
FIG. 12(a) is a cross section of FIG. 13(a), as viewed from the left.
A two-pronged bracket 12 is mounted on the device unit 7. As shown in FIG. 12(b), the universal joint 50 comprises the two-pronged bracket 12, a tilting bridge member 13, a support shaft 9, and a support shaft 10. The tilting bridge member 13 is provided to the two-pronged bracket 12 through the agency of the support shaft 10. The operating lever 6 is provided to the tilting bridge member 13 through the agency of the support shaft 9. Specifically, the operating lever 6 is mounted on the device unit 7 through the agency of the universal joint 50.
The support shaft 9 of the universal joint 50 is provided such that the axis thereof is orthogonal to the axis of the support shaft 10.
The support shaft 9 is parallel to the upper surface of the mounting plate 11 and is at a right angle to the plane of paper. The support shaft 9 supports the operating lever 6 while allowing it to rotate about the support shaft 9. Specifically, the operating lever 6 can be tilted to the right and left in FIG. 12(a) by being rotated about the support shaft 9.
The support shaft 10 is parallel to the upper surface of the mounting plate 11 and is at a right angle to the aforementioned support shaft 9. The support shaft 10 supports the tilting bridge member 13 in the two-pronged bracket 12 while allowing the member to rotate about the support shaft 10. Specifically, the operating lever 6 can be tilted in the direction orthogonal to the plane of paper in FIG. 12(a) by being rotated together with the tilting bridge member 13 about the support shaft 10.
Adopting this configuration for the universal joint 50 allows the operating lever 6 to be tilted in relation to the device unit 7 in two directions at right angles to each other.
The disk plate 8 is mounted on the operating lever 6 such that the tips (tops) of the pistons 1, 2, 3, and 4 come into contact with the lower surface of the plate.
The pistons 2 and 4 can therefore be displaced in accordance with the direction and amount of tilt of the operating lever 6. Although this is not shown in FIG. 12(a), the same applies to the pistons 1 and 3.
The device unit 7 is equipped with hydraulic signal generation means for generating hydraulic signals whose magnitude corresponds to piston displacement for each of the four pistons 4, 2, 1, and 3. The pistons 4, 2, 1, and 3 correspond to pilot ducts 14, 15, 16, and 17, respectively (see FIG. 13(b)).
The operation of the above-described operating lever device 5 will now be described.
FIG. 12(a) depicts the operating lever 6 in the neutral position. From this state, the operating lever 6 is tilted (to the left in the drawing) about the support shaft 9. When this is done, the piston 4 on the left side of the drawing is pressed down in the direction of arrow A through the agency of the disk plate 8.
When the piston 4 is depressed, the pilot duct 14 outputs a hydraulic pilot pressure P.sub.p whose magnitude is proportional to the amount of tilt of the operating lever 6. Similarly, hydraulic signals indicating pilot pressure P.sub.p are outputted from the pilot ducts 15, 16, and 17 when the pistons 2, 1, and 3 are displaced in accordance with the tilt of the operating lever 6.
FIGS. 10 and 11 depict two main types of operating pattern concerning the relation between the direction of tilt of the operating lever 6 and the direction of travel of the vehicle.
FIG. 10 is an operating pattern, primarily for a vehicle such as a skid steer loader. The arrows in the drawing indicate the directions in which the vehicle is caused to travel in accordance with the direction of tilt of the operating lever 6.
It is assumed here that the operating lever 6 is tilted forward (rectilinearly) from the neutral position in the F-direction, as shown in FIG. 10.
At this time, the piston 4 alone is displaced in the operating lever device 5. Consequently, a hydraulic signal P.sub.p is outputted from the pilot duct 14 alone. A hydraulic actuator (not shown) operates in accordance with the hydraulic signal P.sub.p, propelling the vehicle forward (rectilinearly).
As shown in FIG. 10, the vehicle is propelled backward (rectilinearly) when the operating lever 6 is tilted backward in the B-direction. In addition, the vehicle is caused to make a right spin-turn (pirouette) when the operating lever 6 is tilted in the R-direction, which corresponds to a right spin-turn (pirouette). The vehicle is caused to make a left spin-turn (pirouette) when the operating lever 6 is tilted in the L-direction, which corresponds to a left spin-turn (pirouette). Tilting the operating lever 6 in a direction intermediate between the F-direction and R-direction will cause the vehicle to turn right while moving forward. Tilting the operating lever 6 in a direction intermediate between the R-direction and B-direction will cause the vehicle to turn right while moving backward. Tilting the operating lever 6 in a direction intermediate between the B-direction and L-direction will cause the vehicle to turn left while moving backward. Tilting the operating lever 6 in a direction intermediate between the L-direction and F-direction will cause the vehicle to turn left while moving forward.
FIG. 11 is an operating pattern, primarily for a vehicle such as a bulldozer.
As shown in FIG. 11, the vehicle is propelled forward (rectilinearly) when the operating lever 6 is tilted forward in the F-direction. In addition, the vehicle is propelled backward (rectilinearly) when the operating lever 6 is tilted backward in the B-direction. The vehicle stops when the operating lever 6 is tilted right in the R-direction. The vehicle stops when the operating lever 6 is tilted left in the L-direction. Tilting the operating lever 6 in a direction intermediate between the F-direction and R-direction will cause the vehicle to turn right while moving forward. Tilting the operating lever 6 in a direction intermediate between the R-direction and B-direction will cause the vehicle to turn left while moving backward. Tilting the operating lever 6 in a direction intermediate between the B-direction and L-direction will cause the vehicle to turn right while moving backward. Tilting the operating lever 6 in a direction intermediate between the L-direction and F-direction will cause the vehicle to turn left while moving forward.
In the conventional operating lever 6 depicted in FIGS. 12(a) and 12(b), the pistons press on the disk plate 8 with the spring force of return springs 43 and 44, and the operating lever 6 automatically returns to the neutral position when the operator moves the lever to the prescribed operating position and then releases the lever.
The requirement in this case is that the vehicle continue moving even when the operating lever 6 is released. Specifically, the operator may perform various other operations and procedures besides moving the operating lever. It is necessary, however, to maintain the operating lever 6 in a constant state even when other operations are being performed. The operator is under considerable stress because of the need to perform a plurality of operations at the same time. Specifically, it is required that the operating lever 6 be kept in the same operating position to reduce operator stress.
It has been proposed to preserve a tilted position of the operating lever 6 in order to allow a vehicle to continue to travel even when the hand has been removed from the lever.
FIG. 14 depicts an operating lever device 5' capable of automatically maintaining the operating lever 6 in a constant operating position.
The operating lever device 5' depicted in FIG. 14 differs from the operating lever device 5 depicted in FIGS. 12(a) and 12(b) in that the operating lever device 5' can operate only in the longitudinal or transverse direction (for example, longitudinal direction).
In FIG. 14, the operating lever 6 is supported by a support shaft 91 while allowed to tilt solely in a direction parallel to the plane of paper.
A sliding surface 6b of prescribed curvature is formed on the base portion 6a of the operating lever 6. The operating lever device 5' is provided with a brake member 90 having a sliding surface whose shape corresponds to the shape of the sliding surface 6b of the aforementioned operating lever base portion 6a. Depressing the brake member 90 with a rod 92 brings the sliding surface of the brake member 90 and the sliding surface 6b of the operating lever base portion 6a into contact with each other. The other structural elements are the same as in FIG. 12(a), and will therefore be omitted from the description.
FIG. 14 depicts a state in which the operating lever 6 is in a neutral position. Let us assume that the operating lever 6 is tilted from this state forward in the F-direction on the left side of the drawing about the support shaft 91. When this is done, the piston 4 on the left side of the drawing is depressed in the direction of arrow A through the agency of the operating lever base portion 6a.
When the piston 4 is depressed, the pilot duct 14 outputs a hydraulic pilot pressure P.sub.p whose magnitude is proportional to the amount of tilt of the operating lever 6. A hydraulic actuator (not shown) is thereby operated, and the vehicle is propelled forward. A hydraulic signal indicating pilot pressure P.sub.p is outputted by the pilot duct 15, and the vehicle is propelled backward in a similar manner when the piston 2 on the opposite side is displaced in proportion to the tilt of the operating lever 6.
In this case, frictional force based on the sliding resistance between the sliding surface 6b of the operating lever and the brake member 90 overcomes the rotational return force exerted by the return springs 43 and 44, and the operating lever base portion 6a remains in a prescribed rotational position when the operating lever 6 is released by the operator after the lever has been moved to a prescribed operating position and the operating lever base portion 6a rotated to the prescribed rotational position. The operating lever 6 is thus held in the state existing in the prescribed operating position.
The operating lever device depicted in FIG. 14 preserves the signal output state thereof as a result of lever position holding.
The operating lever device 5 depicted in FIG. 12(a) and designed for operation with both directional components (longitudinal and transverse directions) is similar to the operating lever device 5' in FIG. 14 designed for operation with a single directional component in that the requirement is still to preserve the signal output and to reduce operator stress.
When released, however, the operating lever device 5 depicted in FIG. 12(a) automatically returns to the neutral position.
The operator in control of the operating lever device 5 depicted in FIG. 12(a) is required to lock in the operating lever 6 and to preserve the current signal output state only with respect to a single directional component selected from the directional components related to longitudinal and transverse directions.
There are, for example, cases in which the operator needs to move the operating lever 6 in a direction intermediate between the forward direction and the right-hand direction and to drive the vehicle forward while turning it to the right in the manner shown in FIGS. 10 and 11, and to subsequently propel the vehicle forward while preserving the current travel speed.
If it is assumed that the conventional technology illustrated in FIG. 14 is used and the operating lever 6 is released after the vehicle has been propelled forward while being turned to the right, the vehicle will still continue to move forward while turning to the right because the operating lever 6 is held in the operating position achieved at the time of release.
A first object of the present invention is to preserve the operating position and to maintain the correspond signal output state only with respect to one directional component selected from among the directional components of the longitudinal and transverse directions, even when the operating lever is tilted using components of both the longitudinal and the transverse directions.
It should also be noted that the holding function whereby the operating lever is held in a tilted position and the signal output state thereof is preserved sometimes needs to be canceled in certain operating situations.
An arrangement in which the operating lever is held in a tilted position has the following disadvantages.
Let us assume that the engine has stopped with the operating lever held in a tilted position. When the engine is restarted in this state, the vehicle is jolted forward in accordance with the tilting direction of the operating lever.
A second object of the present invention is to make it possible to cancel the holding function whereby the operating lever is held in a tilted position and the signal output state thereof is preserved.